Field of the Invention
The present invention relates to an image processing apparatus and a method for estimating an error in registration between images.
Description of the Related Art
In an image diagnosis using medical images (three-dimensional tomographic images that represent information within an object), a doctor performs a diagnosis while comparing images captured by a plurality of image capturing apparatuses (modalities), differing positions, times, image capturing parameters, or the like. However, when the posture or the shape of an object differs between images, it is difficult to perform an identification and comparison of a lesion portion between images. Accordingly, by performing a registration between a plurality of images, generation of an image that is made to be the same as another one by applying a deformation or a transformation of a posture in the one image is attempted. Also, it is possible to calculate and present a position of a corresponding point, that corresponds to a point of interest on one image, on another image by performing such a registration. As a result, the doctor can easily perform an identification or comparison of a lesion portion between a plurality of images. There are also cases in which similar work having the objective of inspection an internal state of an object is executed in fields other than medicine.
However, because, in general, the result of registration includes an error, and it is not necessarily accurate, there is a problem in that a doctor cannot determine to what degree the result of the registration may be trusted. With respect to this, Japanese Patent Laid-Open No. 2013-198722 (hereinafter referred to as document 1) discloses a method of estimating an error based on an instability (solution uncertainty) of a deformation parameter estimated as a result of a deformable registration. In the method of document 1, based on a range in which an estimation position of a corresponding point for a point of interest varies when an unstable parameter is caused to vary intentionally, an error in this position is estimated.
However, while it is possible to estimate a random error (solution uncertainty) at an arbitrary position based on the instability of an estimation parameter in the method of estimating error recited in document 1, there is the problem that other factors cannot be considered.